1. Field of the Invention
The present invention pertains to a method for the manufacture of vacuum tube bases for which the internal conductors do not have to be cut after moulding, and to a device for the application of this method.
2. Description of the Prior Art
The manufacturing of bases for vacuum tubes usually comprises two distinct stages. Firstly, the pressing stage, which consists in embedding electrical conductors between two pieces of molten glass and secondly, in moulding the unit thus formed so as to obtain a part with a determined geometry and quality, a part which we shall call a "machine-produced base". To do this operation, the metallic conductors are automatically loaded into housings planned for this purpose in bottom moulds. The glass parts are then loaded into this same mould, and then heated up until they become soft. An upper mould is then pressed onto the glass to shape it. The same heating/pressing operation is then repeated three times in order to obtain a good-quality, finished product. During the pressing operation, a set of independent, mobile weights presses on each of the conductors to keep it at the bottom of its housing. The second stage is the finishing stage, which comprises a number of operations, among them, the cutting of the "internal" parts of the conductors to give them the desired length, these internal parts being those that are subsequently connected to the various electrodes of the vacuum tubes and which generally have different lengths. This cutting operation, during the finishing stage, has a certain number of disadvantages, especially as regards the embrittlement of the glass of the base in the sealing zone through the creation of stresses, and as regards the expense and difficulty of maintaining the cutting tools since the conductors are generally nickel based and are therefore difficult to cut.